The derailment happened around 7:30 p.m. off Route 5, forcing 11 of 21 cars to leave the track to some degree, five of them toppling over, said Cynthia Scarano, executive vice president of the Massachusetts-based railroad.

At the time of incident, crews were in the process of breaking down a larger train into a smaller one headed to Deerfield, Mass., Scarano said. The cars that derailed were mostly empty or contained soybeans, Scarano said.

The railroad considers a car derailed when a single wheel leaves the tracks.

Exactly how the derailment happened is still under investigation, but Scarano said it did not involve a collision and occurred at low speed.

The locomotive moving the cars did not derail and contains a black box that investigators will review to help determine the cause of the wreck, she said. No one was injured.

Scarano said crews are in the process of evaluating the damage to the cars and righting those that can be put back on the track.